Pour-Flush Latrines, Latrine Pans, Latrine Pan Assemblies, and Related Methods

ABSTRACT

The invention described herein includes a pour-flush latrine pan mountable at a surface that includes a collection basin and a flapper. The collection basin has an upper bowl portion that tapers to an outlet extending through a wall of the collection basin at its lower end. The flapper includes a counterbalance device and a coverplate disposed on opposite sides of a pivot. The coverplate has a shape adapted to cover the outlet of the collection basin when the coverplate is engaged against the lower end of the collection basin. The flapper is pivotally mounted against the collection basin such that the coverplate engages against the lower end of the collection basin when a pivotal force attributable to the counterbalance device is greater than a pivotal force applied to the coverplate that engages the lower end of the collection basin. In an embodiment, the shape of the coverplate defines a channel that engages the lower end of the collection basin about its perimeter when the coverplate is engaged against the lower end of the collection basin 
     The invention also includes latrine pan assemblies, latrines and methods that employ the latrine pan.

BACKGROUND OF THE INVENTION

It is reported that about 2.5 billion people worldwide do not haveaccess to any type of improved sanitation facility. These individualssuffer significant adverse health effects, including death, as a directresult of a lack of improved sanitation, including toilet facilities.Diarrheal diseases resulting from lack of sanitation are the secondleading cause of child deaths in the world, claiming over 700,000 livesper year. The most affected are individuals residing in developingcountries, often living in conditions of poverty outside of citycenters. Such individuals do not have regular and easy access to arunning fresh water supply or to facilities for the sanitary disposal ofhuman excreta.

Because of the very real dangers posed by poor sanitation, the UnitedNations included access to improved sanitation as part of the MillenniumDevelopment Goals (MDGs) established at the Millennium Summit in 2000.Specifically, Goal 7, Target 7c of the MDGs aspires to reduce by halfthe proportion of people without sustainable access to basic sanitationby the year 2015. “Basic sanitation” requires access to facilities thathygienically separate human excreta from human contact, such as toiletswith sewer connections and septic system connections, where feasible, orpour-flush and covered slab latrines in more remote areas.

Traditional, open pit latrines, bucket latrines, and hanging latrines donot meet the criteria of improved sanitation, in part because thehygienic separation of the actual waste products from human contact isnot ensured, but also because of the unregulated and uncontrolledrelease of various sewage-generated gases from these types of latrines.Gases emitted from the decomposing human waste in a leach pit pose, atminimum, an olfactory challenge, as their odor is unpleasant. Of greatersignificance are the potential adverse health effects of longer termexposure to the sewage gases, in particular to methane, hydrogensulfide, and ammonia. Exposure to these gases, even in low levels overthe long term can result in chronic mucus membrane irritation, causechronic coughing or sore throat, shortness of breath, and fluidaccumulation in the lungs. Other effects may include fatigue, pneumonia,loss of appetite, headaches, irritability, poor memory, and dizziness.At very high concentrations (>300 ppm), hydrogen sulfide can cause lossof consciousness and death.

Pour-flush latrines are considered by the UN and the World HealthOrganization to be suitable, improved sanitation facilities in warmerweather locales where water or sullage is readily available, but sewerpipes and plumbed in toilet facilities are not. Pour-flush latrines areadvantageous as compared to ventilated pit latrines in that they can befitted with a water seal or “trap” that prevents flying insects formentering the pit, thereby blocking transmission of pathogens. Moreover,the portal for a pourflush latrine can be sited at some distance fromthe leach pit, where the excreta is collected and decomposed, since thetransport of the excreta to the leach pit is not wholly reliant ongravity. For example, the squatting plate can bear a waste portal whichis connected to the leach pit via a pipe, and the excreta are pushedthrough the pipe by a water/sullage stream which has been poured intothe portal by the user.

Pour-latrines require a low water volume (1-3 liters per “flush”), aresuitable in cultures where anal cleansing traditions are prevalent,require minimum maintenance, can be sited in family residences andoperated using sullage (as opposed to fresh water), effectively solvingtwo problems (proper excreta and sullage disposal) with one device.

In most latrines, including pour-flush latrines, once the excreta isdelivered to the leach pit, it is degraded by aerobic and anaerobicmeans, and will necessarily generate a variety of gases, many of whichsmell unpleasant, and some which are harmful to one's health. To preventor ameliorate emission of sewage gases back into the squat hole room orliving space where the waste portal is located, prior art pour-flushlatrines have relied upon a variety of structural modifications:well-fitted squat hole covers, U-bend water seals (for example, a U-bendtrap in a pipe connecting the squat hole and the leach pit) or use ofsquat pans having gooseneck-shaped pipe outlets, which discourage “backflow” of gases from the leach pit.

However, these solutions have a variety of disadvantages. Squat holecovers are only effective if replaced diligently and if the tight sealbetween the squat hole perimeter and the cover can be maintained, whichis difficult in a non-climate controlled environments. U-bend pipe waterseals and gooseneck shaped pipe outlets frequently and regularly becomeblocked by the bulky anal cleansing materials (cardboard, grasses,leaves, maize cobs, vegetable peels, cement bags, rags, etc.) utilizedin the absence of Western-style toilet paper, resulting in sewage backupor a reversion to non-sanitized waste disposal methods. They alsorequire a larger volume of water to completely flush excreta to the pit.

A typical 3 inch (7.6 centimeter) diameter plastic U-bend fitting has aninternal volume approaching one liter. When waste is deposited in theU-bend, several liters of water can be required to completely flush itto the pit. Although water may be located nearby the latrine, theinconvenience of carrying large quantities can deter users fromoperating the latrine to the full extent of its hygienic potential.

Thus, there remains a need in the art for latrines and latrine pans thatcan be inexpensively produced and distributed, that reduce the potentialfor pathogen transmission through flying insects, reduce or preventbackflow of sewage gases, require minimal water for flushing, and areeasy to maintain and use.

BRIEF SUMMARY OF THE INVENTION

The invention described herein includes a pour-flush latrine panmountable at a surface that includes a collection basin and a flapper.The collection basin has an upper bowl portion that tapers to an outletextending through a wall of the collection basin at its lower end. Theflapper includes a counterbalance device and a coverplate disposed onopposite sides of a pivot. The coverplate has a shape adapted to coverthe outlet of the collection basin when the coverplate is engagedagainst the lower end of the collection basin. The flapper is pivotallymounted against the collection basin such that the coverplate engagesagainst the lower end of the collection basin when a pivotal forceattributable to the counterbalance device is greater than a pivotalforce applied to the coverplate that engages the lower end of thecollection basin. In an embodiment, the shape of the coverplate definesa channel that engages the lower end of the collection basin about itsperimeter when the coverplate is engaged against the lower end of thecollection basin

The invention also includes latrine pan assemblies, latrines and methodsthat employ the latrine pan.

Also included within the scope of the invention are pour-flush latrinesand latrine pan assemblies for installation into a pour-flush latrinethat include the above described latrine pan and water dispensingvessel.

Methods of preventing or reducing a flow of a sewage gas from a leachpit, methods of reducing the incidence of adverse health effects causedby sewage gas exposure in a latrine-using individual and methods ofsustainably and hygienically removing human excreta from human contactare also included within the scope of the invention.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The foregoing summary, as well as the following detailed description ofembodiments of the invention, will be better understood when read inconjunction with the appended drawings. For the purpose of illustratingthe invention, there is shown in the drawings embodiments which may bepreferred. It should be understood, however, that the invention is notlimited to the precise arrangements and instrumentalities shown. In thedrawings:

FIG. 1, which includes FIGS. 1A and 1B, is a perspective view of thepour-flush latrine pan of the invention, in the “closed” and the “open”position respectively;

FIG. 2, which includes FIGS. 2A and 2B, is a side view of the pour-flushlatrine of the invention, in the “closed” and the “open” positionrespectively;

FIG. 3, which includes FIGS. 3A and 3B, is a top plan view of thepour-flush latrine of the invention, in the “closed” and the “open”position respectively;

FIG. 4, which includes FIGS. 4A and 4B, is a bottom plan view of thepour-flush latrine of the invention, in the “closed” and the “open”position respectively;

FIG. 5, which includes FIGS. 5A and 5B, is a front view of thepour-flush latrine of the invention, in the “closed” and the “open”position respectively;

FIG. 6, which includes FIGS. 6A and 6B, is a back view of the pour-flushlatrine of the invention, in the “closed” and the “open” positionrespectively;

FIG. 7 is an embodiment of a flapper to be used with the latrine pan ofthe invention;

FIG. 8 is a detail view of the lower end of the basin and the coverplateof the latrine pan of the invention;

FIG. 9 is a detail side view of the latrine pan of the invention;

FIG. 10 is a detail view of the interior of the lower end of the basinwhen the coverplate is engaged against the lower end;

FIG. 11 illustrates component parts of the latrine pan assembly of theinvention;

FIG. 12, including FIGS. 12A, 12B and 12C, shows a cross section of thelatrine pan of the invention in the serial steps of an open/close cycleof the flapper;

FIG. 13 includes FIGS. 13A and 13B. FIG. 13A is a top plan view of thelatrine of the invention installed in a cement slab FIG. 13B illustratesa cross section of the latrine pan and slab installment taken at X-X₁ ofFIG. 13A;

FIG. 14 is a schematic representation of a closed pit latrine of theinvention shown in cross section; and

FIG. 15 is a schematic of representation of a pour-flush latrine of theinvention shown in cross section, wherein the latrine pan is remotelylocated from the leach pit.

DETAILED DESCRIPTION OF THE INVENTION

The invention described herein includes a pour-flush latrine pan thatcan be mass produced and transported to remote areas at relatively lowcost, is resistant to blockage under everyday use when installed as partof a latrine, prevents flying insects from passing in and out of thepit, and prevents or reduces the backflow of sewage gases from the leachpit into the squatting room or residence in which the pour-flush latrineis sited. Also contemplated within the scope of the invention arepour-flush latrine pans and assemblies, pour-flush latrines, methods ofreducing the incidence of adverse health effects, methods of preventingor ameliorating the flow of sewage gases, such as hydrogen sulfide orammonia, from a leach pit, methods of installing the pour flush latrinepan, and methods of sustainably and hygienically removing human excretafrom human contact. Each aspect of the invention is described in detailbelow.

The invention in some embodiments will be described with reference tothe drawings provided herein. In the specification, words such as“inner” and “outer,” “upper” and “lower,” “superior” and “inferior,”“distal” and “proximal”, “inwardly” and “outwardly,” and “uppermost” and“lowermost,” and words of similar import are used for assisting in theunderstanding of the invention when referring to the drawings and absenta specific definition or meaning otherwise given by the specificationfor such terms, should not be considered limiting to the scope of theinvention.

The invention includes a pour-flush latrine pan that includes acollection basin and a flapper. The collection basin may be of any size,design or shape known or to be developed in the art. For example, thecollection basin design may be circular, oval, square, kidney-shaped ortriangular when regarded in plan view. As will be understood in the art,numerous “squat pan” designs have been developed based upon cultural andhabitual preferences and any of these designs may be employed in thepresent invention. Regardless of the specific shape, it may be preferredthat the design/shape of the collection basin be adapted to reducingurine splashing, facilitate flushing of excreta and sanitary productswith minimal water flow, permit assumption of a comfortable collectionposition by adults, and/or be on a scale that can be safely used bychildren.

Depending on the social or cultural preferences in the locale in whichthe latrine pan is to be used, the collection basin may be formed as atoilet stool (i.e., a structure that facilitates defecation whilesitting) or a squat pan (i.e., a structure used in areas where thepreference is to defecate while squatting).

In an embodiment, the collection basin is formed as a squat pan andincludes a bowl having a radially extending elongated portion, such thatthe collection basin's top plan view resembles a stylized pear-shape(see, e.g. FIG. 3A). In this embodiment, it may be preferred that theelongated portion extends from the upper bowl portion only, so that thecollection basin has a non-uniform depth, with the bowl of the basinthrough which the outlet extends, being the deeper.

It may be preferred that the collection basin has a capacity of about 3to about 15 liters, to ensure safe and spill-less receipt of human wasteand of the flush water. In an embodiment, it may be preferred that thecollection basin has a length dimension of about 9 inches (23centimeters) to about 22 inches (56 centimeters) and, independently, thewidth dimension may be about 6 inches (15 centimeters) to about 16inches (41 centimeters). Smaller sizes within this range would bedesirable for application where primary use by children is foreseeable,such as in schools.

The collection basin may be manufactured as an integral piece or it maybe manufactured in components (of the same or of different materials)that are subsequently assembled. The collection basin may be cast,molded, thermoformed, stamped, carved or otherwise formed, depending onthe material selected. Any material known or to be developed in the artmay be used, such as, without limitation, a polymer, a plastic, acomposite, a metal, a concrete, a cement, a natural or synthetic stone,a composite, a wood, a fiberglass, a marble, a porcelain, a ceramic,gravel, and a clay. It is preferred that the material selected isdurable, resistant to crazing, and smooth surfaced.

The collection basin may be formed of a first material, and then coatedwith one or more of a second material to realize desirable surfaceproperties. For example, the collection basin may be made of afiberglass material that is coated with a non-stick polymer (for examplepolytetrafluoroethylene (TEFLON®)) to increase the ability to maintain aclean, excreta-free surface or an antibacterial coating, such asnanoparticles of titanium dioxide, silver, copper, gold, and/or gallium.

In some embodiments, the material of the collection basin is athermoplastic or thermoset polymer or copolymer as such materials aredurable, relatively inexpensive and easy to fabricate and to clean.Suitable plastics may include polyethylene terephthalate, high-densitypolyethylene, polyvinyl chloride, low-density polyethylene,polypropylene, polystyrene, polyvinylidene chloride, high impactpolystyrene, polyamides, acrylonitrile butadiene styrene,polyethylene/acrylonitrile butadiene styrene, polycarbonate,polycarbonate/acrylonitrile butadiene styrene, polyurethanes, melamineformaldehyde, phenolics, polyetheretherketone, polyetherimide,polymethyl methacrylate, polytetrafluoroethylene, and/orurea-formaldehyde.

Regardless of the shape or size selected, the collection basin includesa bowl, an upper portion of which having walls that taper downwardly toan outlet. The outlet extends through a wall of the basin, preferably awall in the lower end of the basin. The slope of the taper may be steepor gradual, depending on the design and shape of the overall collectionbasin. Preferably, as noted above, the slope is adjusted to minimizesplashing from the sidewalls and to facilitate progress of excreta andother waste through the outlet.

The outlet may be, for example, a simple hole defined by the lowermostsidewall of the basin or a conduit defined by the narrowing of the basinsidewalls of the lower end of the basin. In some embodiments, the outletis defined by a structure that is adapted to be fitted to pipe orconduit, so that the latrine pan and the leach pit may be sited apartbut remain in fluid communication. In an embodiment, the outlet has adiameter of about 10 cm to about 20 cm, although outlets of anydimension may be used. However, the most suitable dimension is one largeenough to permit egress of the non-standard toilet paper substitutesused in the region where the latrine is to be installed but not so largethat it poses a danger to small children.

The pour-flush latrine pan of the invention also includes a flapper. Theflapper itself includes a counterbalance device and a coverplate thatare disposed on opposite sides of a pivot relative to one another. Asnoted with the collection basin, the flapper can be manufactured as onepiece or as several pieces that are subsequently assembled together. Theflapper or its component parts may be made of any of the materialsdiscussed above as suitable for the collection basin, including coatingsand additional surface treatments.

The coverplate is adapted to cover the outlet of the collection basinwhen the coverplate is engaged against the lower end of the collectionbasin. If the outlet has a substantially circular cross section, it maybe preferred that the coverplate is disc shaped, or modified-disc shaped(that is, discs with radial extensions, flanges, lips, etc.) and is of adiameter that is at least slightly greater than the diameter of theoutlet, so that when the coverplate is engaged against the lower end ofthe collection basin the outlet is fully covered.

To provide a liquid seal that prevents, reduces or ameliorates thepassage of sewage gases and flying insects from one side of the coverplate (e.g., the side in communication with the leach pit) to the otherside (e.g., the side in communication with the environment of thesquatting room), it may be preferred that the coverplate has a shapethat engages and folds upwardly around a lower end of the collectionbasin, thereby forming a receptacle or channel for collecting a portionof flush water. The flush water that remains on the cover plate afterclosure of the flapper creates an airtight liquid seal between thecollection basin and the coverplate of the lapper.

The reliability of the seal can be improved by ensuring that anyremaining flush water is directed towards the interface of the outlet ofthe collection basin and the flapper. Thus, it is preferred to form achannel around the perimeter of the coverplate. The channel may engagethe entire perimeter of the lower end, or only a portion of theperimeter of the lower end.

Additionally, in an embodiment, the coverplate may contain a convexportion that extends within the outlet of the collection basin when thecoverplate is engaged against the lower end of the collection basin. Theconvex portion reduces the depth of water collected in the coverplate,thereby reducing upward splashing of water during use. The convexportion also facilities proper alignment/re-alignment of the channel andthe lower end of the basin after an open/close cycle of the flapper. Insome embodiment, the rise of the convex portion may serve as a wall ofthe channel.

Under everyday use of the pour-flush latrine pan, several milliliters offlush liquid will remain residing in the channel after flushing, forminga liquid seal between the surface of the coverplate and the lower end ofthe basin. The seal serves to prevent, reduce and/or ameliorate thebackflow of gases from the leach pit into the environment of theresidence or squatting room. Such reduction may be at least by 50%, by80% or by 90% or more as compared to an uncovered leach pit.Advantageously, the seal may also prevent entry of most types of insectsinto the human environment or into the leach pit, blocking a majortransmission route for diarrheal diseases.

In an embodiment of the invention, the channel is designed to captureand retain a minimal amount of liquid—enough to create a functionalseal, but not enough to give rise to excessive splashing during use, andnot enough to require use of an extremely large counterweight whichwould place unnecessary stress on the hinge of the flapper. In anembodiment, it may be desired that the channel is designed to containabout 5 mls to about 200 mls. It may be preferred that the amount ofwater present is about 125 mls.

When using the latrine pan, the flapper is pivotally mounted against thecollection basin. The coverplate and a counterbalance device aredisposed on opposite sides of the pivot. The coverplate is placed sothat it covers the outlet, as described above, and on the other side ofthe pivot is located the counterbalance device. The flapper “teetertotters” between a closed state (where the coverplate is engaged againstthe lower end of the basin) and an open state (where the coverplate andthe lower end disengaged and spaced apart to permit egress of excretaand other waste into the leach pit). Whether the flapper is in an “open”or a “closed” state depends on which end of the flapper is exerting thegreater pivotal force.

Specifically, the counterbalance device serves to maintain the closedstate of the flapper by exerting a pivotal force that is greater thanany counter pivotal force applied to the coverplate either: (1) when thecoverplate is vacant (and/or contains water for the water seal) or (2)when the coverplate bears excreta or other waste. The counterbalancedevice must have a mass that exerts a pivotal force that is greater thanor equal to the pivotal force exerted by an average excreta quantity,but not greater than the force exerted by a hand poured water stream. Aswill be appreciated in the art, such mass will vary depending on thelocation of the pivot relative to the counterbalance device, but anysuch adjustments are well within the purview of a person of ordinaryskill in the art and/or common sense.

In an embodiment, the pivot is substantially equidistant between thecoverplate and the counterbalance device, and the center of mass of thecounterbalance device or the coverplate is about 5 to about 20centimeters from the pivot.

In a simple iteration, the counterbalance device may be any material ofsufficient mass or weight (“weight material”) secured to the flapper,either during manufacture or post-manufacture. For example, thecounterbalance device may be a rock, brick or block of suitable sized ormass found on site as the latrine is constructed that is affixed to theflapper.

In an embodiment, the counterbalance device is a container (eitherintegral with or affixed to) the flapper, that can be filled with aweight material. This affords the advantage of eliminating unnecessaryweight to the latrine pan while it is in transit to the remote locationwhere the latrine is to be built. As latrine construction almost alwaysutilizes cast concrete for one application or another, as in forexample, the formation of the floor or slab that holds the latrinepan/collection basin, it is particularly advantageous and convenient touse concrete as the counterweight material.

In such embodiment, it may be preferred that the container is selectedfrom a cube, a rectangular prism, a sphere or a similar shape. In anembodiment, the container is a cup shape or a hollow cylinder that isfilled with a weight material chosen from, without limitation, cement,concrete, asphalt, sand, water, stones, pebbles, metal, particulates,wood and mixtures thereof. It may be a closed container or an opencontainer. When using concrete or another material that sets or cures toform a solid body, it may be advantageous to form one or more outwardprotrusions extending from the walls of the container. These protrusionsmay serve to mechanically lock the section of cured concrete within thecup, yet can be formed from injection molded plastic without locking thepart onto the tool. In an embodiment, the protrusions extend about 1 mmfrom the interior sidewalls of the container.

It some embodiments, it may also be preferred that that the legendCONCRETE is molded into the container. The English word “concrete” isrecognized and understood in many countries, even those where Englishmay not be routinely written or spoken. Alternatively, one can print ortape the legend CONCRETE on the container.

As noted above, the amount of weight material will vary depending on theamount of pivotal force that the counterbalance device must exert. Thevolumetric dimensions of the container will necessarily vary dependingon the amount or type of weight material that is required in a specificlatrine application. It may be preferred that the container hasvolumetric dimensions (that is, be of a size) to contain an amount ofweight material sufficient to exert a pivotal force upon the flapperthat is greater than a pivotal force exerted on the flapper by anaverage excreta quantity when the average excreta quantity rests and/ormakes impact with the coverplate when delivered by gravity from a pointabout 40 to about 70 centimeters from the surface of the coverplate. By“average excreta quantity” it is meant about one average bowel movementfrom a reasonably healthy individual suffering from no significantgastrointestinal disorders.

In an embodiment, the container may have volumetric dimensions tocontain an amount of weight material sufficient to exert a pivotal forcethat is greater than a pivotal force exerted by about 0.5 to about 3average excreta quantities when the average excreta quantities restand/or makes impact the coverplate. When the counterweight exerts apivotal force that is less than the weight of the excreta deposited inthe flapper, the flapper will automatically open to allow the excreta tofall into the latrine pit. If the counterweight exerts a pivotal forcethat is greater than the weight of the excreta deposited in the flapper,the act of pouring flush water should apply sufficient force on theflapper to move it to the open position and empty the collection basin.

As a non-limiting example, the amount of weight material may range fromabout 50 grams to about 1500 grams, more specifically, about 60 grams,about 85 grams, about 100 grams, about 130 grams, about 250 grams, about500 grams, about 750 grams, about 1000 grams, about 1300 grams and about1500 grams.

The flapper is pivotally mounted against the collection basin so thatthe coverplate engages against the lower end of the basin. The flappermay be pivotally mounted directly to the basin (for example, to itsexterior), or it may be mounted on a nearby structure (such as a wall orpost). The pivot may take the form of any known or to be developed inthe art. For example, without limitation, the pivot may be anarrangement of aligned holes in the flapper and the basin and pins; theflapper may include a loop through which a baton is inserted, allowingfor pivotal rotation; the pivot may be a flexible bracket on theunderside of the basin through which the flapper is threaded, or thepivot may be a fulcrum inserted beneath the flapper.

A non-limiting embodiment of the latrine pan and the latrine panassembly included in the invention is illustrated in FIGS. 1 to 13. Withreference to these Figures, a pour-flush latrine pan 100 that includes acollection basin 102 and a flapper 104 is shown. The collection basin102 includes an upper bowl portion 108 having an upper edge 154, whichincludes a flange 140 that encircles the perimeter of the upper edge154. Upon installation of the pour-flush latrine pan 100 into a cementapron or slab 170, the flange 140 is substantially co-planar with thesurface 160 of the slab 170. In these illustrative Figures, the flange140 is shown as extending around the entire perimeter; in practice theflange may extend for only a portion or several discontinuous portionsof the perimeter or be wholly absent.

The bowl 107 of the collection basin 102 includes an upper bowl portion108 that includes an interior wall 120 that tapers downwardly to anoutlet 112 that extends through the basin's wall at a lower end 116 ofthe collection basin 102.

The pour-flush latrine pan 100 further includes a flapper 104 that inturn includes a coverplate 106 and a counterbalance device 118 that aredisposed on opposite sides of a pivot 122. In the embodiment shown inthe Figures, the flapper 104 is pivotally mounted to the exterior 152 ofthe collection basin 102. The pivot 122 is an aligned holes-and-pinconfiguration; a first set of holes 147, 147′ (not shown) extendsthrough an extension body 146 of the flapper 104, and a second set ofholes 148, 148′ (not shown) are present in a spaced bracket 150, 150′ onthe exterior 152 of the collection basin 102.

In the closed state, the flapper 104 causes the coverplate 106 to engageagainst the lower end 116 of the collection basin 102 covering theoutlet 112. The outlet 112 has a circular cross section; thus thecoverplate 106 is substantially disk shaped so as to be adapted to coverthe outlet 112 when the coverplate 106 is engaged against the lower end116 of the collection basin 102. The coverplate 106 includes a centeredconvex portion 136, a circumferential rim 138, and a lip 168. Thecircumferential rim 138 extends above the lower end 116 of thecollection basin 102 basin when the flapper 104 is in the closedposition and serves to hold a portion of flush water within thecoverplate and create an airtight seal.

A channel 104 is also included in the coverplate 106. During use, thechannel 104 assures that a quantity of the residual pour-flush liquid isdirected to the perimeter of the coverplate to form a liquid seal 128between the coverplate 106 and the lower end 116 of the collection basin102.

The flapper 104 also includes a counterbalance device 118 that isillustrated as a hollow cup or cylinder 162. It can be filled with aweight material 161 that is cement as the latrine pan is prepared forsite installation.

The latrine assemblies that may be provided to latrine builders orhouseholders include the latrine pans described herein, as well as awater dispensing vessel, and other optional article, includingcommunication or written materials. In the embodiment illustrated inFIG. 11, the assembly includes a spouted water dispensing vessel 174 anda communication device 172 that is written installation instructions.

A latrine of the invention employing the latrine pan as describe hereincan be sited in a public structure, such a marketplace public facility,a family residence or may be situated outside a family residence is aseparate superstructure (a so-called “outhouse”). Preferred dimensionsof the room or structure are about 800 mm by about 1000 mm or greater.The latrine may be configured by locating the latrine pan immediatelyabove a leach pit. The structure and design of leach pits are wellestablished in the art and will vary depending topographical, cultural,and environmental conditions. Such adjustments are well within the skillset of a person of ordinary skill in the art and will not be repeatedherein.

FIG. 14 shows a schematic of a covered pit latrine 188 of the inventionin cross section. The pour-flush latrine pan 100 is situated in a cementslab 170 and enclosed in a latrine shelter 176. The outlet (not visible)of the latrine pan 100 is in communication with the leach pit 126(equipped with an optional vent pipe 190) when the flapper 104 is in anopen state. The user 186 is shown in squat position, using the footbed182 (one shown only, as is cross section) to orient his hind area 184over the outlet. A spouted water dispensing vessel 174 containing flushsullage is at the ready.

Alternatively, a latrine of the invention can be sited at a distancefrom the leach pit but remain in fluid connection with the leach pit. Aschematic of this arrangement is shown in FIG. 15. The latrine 188′includes a latrine structure 176′, which houses the latrine pan 100. Thelatrine pan 100 is in communication with a junction box 192 ofsufficient volume to permit the flapper to toggle between open andclosed states. The a junction box 192 is connected to a pipe 180, whichempties into a leach pit 126′. Depending on the size of the footprintavailable, the latrine pan can be placed about 1 to about 5 meters fromthe leach pit and connected to the leach pit via pipeworks or a junctionbox laid to a correct grade (preferably about 1 in 30). The leach pit ispreferably sealed with the exception of at least one vent, which issited preferably as far from the latrine pan as is feasible. Thejunction box can be formed of any suitable material, including or notlimited to concrete, brick, plastic, metal, clay, glass, etc.

In any latrine configuration an optional latrine pan cover may beprovided to cover the latrine pan when not in use.

Preferably, the latrine pan is fitted into a cavity that issubstantially the same size and shape as the latrine pan, so that thebasin (with the exception of the outlet which should remainunobstructed) is structurally reinforced. Such reinforcement extends thestructural life of the latrine pan and prevents accidental falls intothe leach pit in the event that an individual loses balance and makesbodily contact with the latrine pan. As an example, the cavity may beformed in the earth (when the outlet is connected via pipeworks to aremotely sited leach pit) or in a cement slab. A cement slab can bepreferably cast around the latrine pan to ensure intimate contactbetween the surfaces and strong bonding of the pan to the slab.

During the installation of the latrine pan and the building of thelatrine, it is preferred that the latrine pan is cast into a cement slabof about 2 inches to about 6 inches (5.1 centimeters to 15.2centimeters) in thickness. The slab should be reinforced with metallicwire to increase its strength and longevity. It is also possible tosecure the latrine pan in a cavity formed in a cement slab which alsoserves to seal the leach pit, such that an upper edge of the collectionbasin is substantially flush with the surface of the slab. Toaccommodate such arrangement, the upper bowl portion may include aflange that extends from the uppermost edged of the upper bowl portion.As shown in FIG. 13, when fitted in a cement slab 170, the topmostsurface 110 of the flange 140 is substantially coplanar with the surfaceof the slab. Alternatively, this flange can be positioned below thesurface if concrete is to be cast directly around the pan. This assuresthat the pan will be well bound to the concrete. It is preferred thatthe cement slab has (or is covered with a flooring material that has) asmooth surface that permits free draining. In an embodiment, the slab isconstructed so as to slope towards the latrine pan to permit draining ofany split flushing water.

In an embodiment of the latrine, the backmost edge of the latrine pan islocated at least about 100 mm to about 150 mm from any wall orstructure. Footbeds may be placed on either side of the latrine pan foruser guidance, to ensure that the excreta is delivered as near aspossible to the outlet.

Once installed, the latrine can be easily operated and maintained. Touse the latrine, the user squats over the collection basin of thelatrine pan, first removing the latrine pan cover, if one was present.Since the latrine pan is initially empty except for the small amount ofwater that creates the water seal, the latrine pan is in the closedposition. Preferably in the collection position, the user delivers theexcreta, which is conveyed by gravity to the surface of the coverplate.The latrine remains in a closed position despite the added weight of theexcreta on the coverplate. Ideally, a single purpose water dispensingvessel is maintained in an area near the latrine pan, and contains about1 liter to about 3 liters of water. The water may be non-potable water,such as unpurified river water, sullage or grey water.

Using the water dispensing vessel, the user then “pour-flushes” thelatrine—he pours the water into the latrine pan; the force applied bythe water increases the pivotal force exerted upon the coverplate,exceeding the pivotal force that is (counter)exerted by thecounterbalance device, and cover plate is disengage from the lower edgeof the outlet and is spaced apart from the outlet to permit egress ofthe excreta. Once the excreta have been removed from the coverplate, theflapper returns to closed position. In most instances, sufficient liquidresidue should remain in the pan to create the liquid seal. In the eventthat additional liquid is necessary or the liquid acting as a sealevaporates under hot weather conditions, an additional aliquot of liquidcan be applied to restore it.

During the pour-flush process, the flapper 104 is toggled between the“closed” and the “open” position using balanced/unbalanced pivotalforce. Referencing FIGS. 12A, 12B and 12C, which shows a cross sectionof the latrine pan, the pivotal force F₁ exerted by the counterbalancedevice 118 exceeds both the pivotal force F₂ exerted by the emptycoverplate 106 a and the pivotal force F₃ attributable to a coverplate106 a upon which rests an average excreta quantity 166. The flapper 104remains therefore in the closed position. When a water stream 130 isapplied to the coverplate 106, the pivotal force F₄ attributable to thewater stream (alone or combined with F₃) exceeds F₁ and the flappertransitions to the open state disengaging from the coverplate, allowingthe average excreta quantity 166 to pass from the coverplate 106 a.

The water dispensing vessel used to apply the water stream that flushesthe latrine pan may be any known or to be developed in the art. It mayinclude a bucket, a scoop, a ladle, a pail, a spout-bearing vessel, ahose, and an expandable bladder. In some embodiments, one may preferthat the water dispensing vessel is sized to dispense only apre-determined amount of water, to conserve water and to avoid over-flowof the leach pit. For example the water dispensing vessel may be chosenfrom those that have liquid volume capacity selected from about 1 liter,about 1.5 liters, about 2 liters and about 3-5 liters. A spouted waterdispensing vessel may be preferred.

In practice, the pour-flush latrine pan described herein may beassembled with a water dispensing vessel, and optionally, written ordigital materials and distributed as a latrine pan assembly forinstallation into a pour-flush latrine. The written or digital materialsmay include a communication device that provides at least one of (a)instructions for assembly of the pour-flush latrine pan, (b)instructions for installation of the pour-flush latrine pan, (c)instructions for use of the pour-flush latrine pan assembly, and (d)instructions for maintenance of the pour-flush latrine pan assembly.Such information may be presented in a language and cultural stylesuitable for the area in which the assemblies are to be distributed.

It will be appreciated by those skilled in the art that changes could bemade to the embodiments described above without departing from the broadinventive concept thereof. It is understood, therefore, that thisinvention is not limited to the particular embodiments disclosed, but itis intended to cover modifications within the spirit and scope of thepresent invention as defined by the appended claims.

1. A pour-flush latrine pan mountable at a surface comprising acollection basin and a flapper, the collection basin having an upperbowl portion tapering to an outlet extending through a wall of thecollection basin at a lower end of the collection basin, the flappercomprising a counterbalance device and a coverplate disposed on oppositesides of a pivot, the coverplate having a shape adapted to cover theoutlet of the collection basin when the coverplate is engaged againstthe lower end of the collection basin, the flapper being pivotallymounted against the collection basin such that the coverplate engagesagainst the lower end of the collection basin when a pivotal forceattributable to the counterbalance device is greater than a pivotalforce applied to the coverplate that engages the lower end of thecollection basin.
 2. The pour-flush latrine pan of claim 1, wherein theshape of the coverplate defines a channel that engages the lower end ofthe collection basin about at least a portion of its perimeter when thecoverplate is engaged against the lower end of the collection basin. 3.The pour-flush latrine pan of claim 1, wherein the shape of thecoverplate defines a channel that engages the lower end of thecollection basin about its entire perimeter when then coverplate isengaged against the lower end of the collection basin.
 4. The pour-flushlatrine pan of claim 3, wherein the shape of the coverplate includes aconvex portion that extends within the outlet of the collection basinwhen the coverplate is engaged against the lower end of the collectionbasin.
 5. The pour-flush latrine pan of claim 4, wherein the channelcontains a liquid that forms a liquid seal between a first surface ofthe cover plate and the lower end of the collection basin that preventsor reduces a flow of a sewage gas from a second side of the coverplateto the first side of the coverplate.
 6. The pour-flush latrine pan ofclaim 5, wherein the sewage gas is hydrogen sulfide or ammonia.
 7. Thepour-flush latrine pan of claim 1, wherein the counterbalance devicecomprises a container that is filled with a weight material.
 8. Thepour-flush latrine pan of claim 7, wherein the container has avolumetric dimension that can contain an amount of weight materialsufficient to exert a pivotal force upon the flapper that is greaterthan a pivotal force exerted on the flapper by an average excretaquantity when the average excreta quantity rests upon the coverplate. 9.The pour-flush latrine pan of claim 8, wherein the amount of weightmaterial is selected from about 60 grams, about 85 grams, about 100grams, about 250 grams, about 500 grams, about 750 grams, about 1000grams, about 1300 grams and about 1500 grams, and the weight material iscement.
 10. The pour-flush latrine pan of claim 8, wherein the containeris a hollow cylinder and the weight material is selected from cement,concrete, asphalt, sand, water, stones, pebbles, metal, particulates,and wood.
 11. The pour-flush latrine pan of claim 1, wherein thecoverplate includes a circumferential rim that extends above the lowerend of the collection basin about at least a portion of its perimeterwhen then coverplate is engaged against the lower end of the collectionbasin.
 12. The pour-flush latrine pan of claim 1, wherein the coverplateincludes a circumferential rim that extends above the lower end of thecollection basin about its entire perimeter when then coverplate isengaged against the lower end of the collection basin.
 13. Thepour-flush latrine pan of claim 1, comprising a flange extending aroundthe perimeter of the upper bowl portion.
 14. The pour-flush latrine panof claim 1, wherein the upper bowl portion includes an elongated portionextending radially therefrom.
 15. The pour-flush latrine pan of claim14, wherein the entirety of the interior of the bowl portion tapersdownwardly toward the outlet.
 16. The pour-flush latrine pan of claim 1,wherein the flapper is pivotally mounted to the exterior of thecollection basin.
 17. The pour-flush latrine pan of claim 1, wherein thepivot of the flapper is a pair of pins extending laterally away from anextension body of the flapper, the counterbalance device and coverplatebeing mounted on opposite ends of the flapper body, the pins engaging apair of aligned holes on a pair of spaced brackets on the exterior ofthe collection basin.
 18. The pour-flush latrine pan of claim 1, whereinthe pivot of the flapper is at least one hole extending laterallythrough an elongate body of the flapper, the counterbalance device andcoverplate being mounted on opposite ends of the flapper body, each holeengaging a pin extending from the exterior of the collection basin. 19.The pour-flush latrine pan of claim 1, wherein the pivot of the flapperis at least one hole extending laterally through an extension body ofthe flapper, the counterbalance device and coverplate being mounted onopposite ends of the flapper body, each hole engaging a pin that alsoengages a pair of aligned holes on a pair of spaced brackets on theexterior of the collection basin.
 20. The pour-flush latrine pan ofclaim 1, installed in a slab such that the upper edge of the upper bowlportion is substantially flush with a surface of the slab.
 21. Thepour-flush latrine pan of claim 1, wherein the collection basin ismanufactured of a material selected from a polymer, a plastic, acomposite, a metal, a concrete, a cement, a natural or synthetic stone,a composite, a wood, a fiberglass, a porcelain, a ceramic, gravel, and aclay.
 22. The pour-flush latrine pan of claim 1, wherein the flapper ismanufactured of a material selected from polymer, a plastic, acomposite, a metal, a concrete, a cement, a natural or synthetic stone,a composite, a wood, a fiberglass, a porcelain, a ceramic, gravel, and aclay.
 23. A pour-flush latrine pan assembly for installation into apour-flush latrine comprising the latrine pan of claim 1 and a waterdispensing vessel.
 24. The assembly of claim 23 wherein the waterdispensing vessel is selected from a bucket, a pail, a spout-bearingvessel, a hose, and an expandable bladder.
 25. The assembly of claim 23,wherein the water dispensing vessel has a liquid capacity selected fromabout 1 liter, about 1.5 liters, about 2 liters and about 3-5 liters.26. The assembly of claim 24, further comprising written materials. 27.The pour-flush latrine pan assembly of claim 26, wherein the writtenmaterials comprise a communication device that provides at least one of(a) instructions for assembly of the pour-flush latrine pan, (b)instructions for installation of the pour-flush latrine pan, (c)instructions for use of the pour-flush latrine pan assembly, and (d)instructions for maintenance of the pour-flush latrine pan assembly. 28.The pour-flush latrine pan assembly of claim 27, wherein thecommunication device comprises text, a drawing, and a cartoon.
 29. Amethod of preventing or reducing a flow of a sewage gas from a leach pitcomprising installing in a slab the pour-flush latrine pan of claim 1.30. The method of claim 29, wherein the flow of the sewage gas isreduced by at least 50% as compared to a conventional open leach pit.31. The method of claim 30, wherein the sewage gas is hydrogen sulfideor ammonia.
 32. A method of reducing the incidence of adverse healtheffects caused by sewage gas exposure in a latrine-using individualcomprising installing over a leach pit the pour-flush latrine pan ofclaim
 1. 33. The method of claim 32, wherein the adverse health effectis chosen from mucus membrane irritation, sore throat, cough, shortnessof breath, respiratory ailments, fluid accumulation in the lungs,fatigue, pneumonia, loss of appetite, headaches, irritability, poormemory, dizziness, loss of consciousness and death.
 34. A method ofinstalling a pour-flush latrine comprising fitting the pour-flushlatrine pan of claim 1 in fluid communication with a leach pit.
 35. Themethod of claim 34, wherein the outlet of the collection basin and theleach pit are separated by at least one meter.
 36. The method of claim34, wherein the pour-flush latrine pan is fitted into a cement slab. 37.The method of claim 34, wherein the cement slab contains a footbed oneither side of the collection basin to facilitate delivery of a bowelmovement as near as possible to the outlet of the basin.
 38. Apour-flush latrine comprising a leach pit in fluid communication withthe latrine pan of claim
 1. 39. The latrine of claim 38, sited in apublic sanitation facility.
 40. The latrine of claim 38, sited in afamily residence.
 41. A method of sustainably and hygienically removinghuman excreta from human contact comprising providing a latrine of claim38; delivering to the coverplate of the latrine pan a bowel movement ofa user, wherein the bowel movement rest upon a first surface of thecoverplate; applying to the bowel movement-bearing coverplate a waterstream such that the pivotal force exerted on the coverplate exceeds thepivotal force exerted on the counterbalance device causing thecoverplate to become disengaged from the lower end of the basin suchthat the coverplate and the lower end are spaced apart sufficiently andthe bowel movement is released from the surface of the cover plate,descending downwardly towards the leach pit; wherein upon release of thebowel movement, the coverplate re-engages against the lower end of thecollection basin and a liquid seal is formed between the first surfaceof the coverplate and the lower end of the collection basin.
 42. Themethod of claim 41, wherein the water stream is applied by manuallypouring water into the collection basin using a water dispensing vessel.